Convert jpt to pnm Online: jpt2pnm

You can use Tom's Editor to easily convert images from
JPEG-2000 Code Stream Syntax .JPT to Portable aNy Map .PNM.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

JPT

JPEG-2000 Code Stream Syntax is an image format with extension JPT.

PNM

PNM images are uncompressed 24 bit RGB images. Can cannot store Alpha channel. PNM images come in 2 types: binary and text. Especially popular on Linux.